20HP Merc - Dies in Forward Only

[Wishin' I Was Fishin']

20 HP Mercury, Approximately a 1978 model <br />The Serial Number is 5608371<br />Can someone verify the year for me please?<br /><br />SYMPTOMS: <br />Engine starts perfectly and idles great and revs up in neutral without hesitation or sputtering. <br /><br />Engine runs flawlessly in reverse and runs at maximum reverse speed without hesitation or sputtering. <br /><br />In forward the engine dies regardless of how slow or fast I try to accelerate. It dies while stuttering like it is starved of fuel but the bulb on the fuel line from the gas tank to the motor is firm and cannot be pumped when the motor is dying.<br /><br />QUESTIONS: <br />This is a tiller controlled motor so the reverse and neutral gear positions do not allow the tiller throttle to be fully opened, this only occurs in forward. It was suggested I may have possible carburetor problems (maybe high speed jet clogged?) I am by no means a mechanic but plan to pull the carburetor and clean it. This could be a scary situation so I am looking for help before beginning this task.<br /><br />What can I do to isolate the problem and/or possibly fix the problem and avoid pulling the carburetor? Could it be the fuel pump? Would a fuel additive possibly help clean the carb if dirty?<br /><br />Thanks.

 

[eurolarva]

Re: 20HP Merc - Dies in Forward Only

Is there something obstructing the lower unit in forward. If you can go in reverse you should be able to go in forward the same speed without motor killing. Carb rebuild is easy. There are only a few parts that come out and go back in. I would pull the plugs and put the motor in forward gear and turn the flywheel clockwise by hand and see if it turns okay. Then put it in reverse and turn the flywheel clockwise and see if the amount of pressure is the same. Make sure battery is disconnected when doing this just to make sure you dont get a spark. I am not that familiar with mercs so make sure the flywheels normal rotation is clockwise. Never turn flywheel in opposite direction. You can test rotation by hitting your starter or seeing which way the rewind starter turns it.

 

[remmer38]

Re: 20HP Merc - Dies in Forward Only

Hi. When you put the motor in gear, the throttle cable moves in proportion to the opening in the carb mouth. Look for the the shift part of the cable to move smoothly. Then look for excessive play in the throttle cable assembly. I replaced a 96 25hp jonnyrudes throttle cable(after drag racin) for 23 bucks. Before I noticed it being hard to throttle up. Guess the plastic cable holder was bound to go. Shame it had to happen against a 90 Mariner with 2 15 year olds Captaining. Now its nice and smooth to throttle. Its not a carb thing and I cant see a starter motor running backwards. Keep us posted.

 

[KCLOST]

Re: 20HP Merc - Dies in Forward Only

remmer, he's got a tiller... Not a cable....